Portable impact tools



m- 12, 6 J. M. FENLIN 3,341,261

v PORTABLE IMPACT TOOLS Filed Jan. 19, 1965 mvsmon John M. Fen/in ATTORNEY United States Patent 3,341,261 PORTABLE IMPACT TOOLS John M. Fenlin, River Bank, Beverly, NJ. 08010 Filed Jan. 19, 1965, Ser. No. 426,650 9 Claims. (Cl. 30633) This invention relates to portable impact tools, and more particularly to an improve-d impact tool comprising a striking head and a tubular plastic handle.

As is known, hand impact tools such as axes, adzes, hatchets and hammers are comprised essentially of a metallic head and a cooperating handle which latter generally is composed of a selected wood such as hickory or ash. The head member embodies a medial section or poll, formed with an eye or socket, and integral terminal portions one of which is a striking head; the other a peening head; in the case of carpenters hammers the peen section is conformed into a semi-crescent shape and is bifurcated to form a claw. The two members of such hammer are assembled into a unit by inserting one end of the handle in the eye of the head and forcing the handle into tight frictional engagement with the head by means of wedges or equivalent spreaders. In recent years the so-called indestructable type hammer has been marketed but this type constitutes but a minor number of hammers produced and used. In this latter type the wooden handle is replaced by a metallic handle member which is formed integrally with the head by welding. Such metallic handles are usually provided with a hand grip section which is covered with some non-metallic shock-absorbing material such as, rubber, leather or selected plastics.

Although an impact tool such as a hammer is of ancient origin and of apparently simple construction it must be carefully constructed to be satisfactory to a skilled artisan. The hammer must, for example, present the proper balance between head and handle and the latter must possess a certain degree of inherent resiliency in addition to satisfactory impact tensile and compressive properties to insure best manipulation of the tool. For these reasons hammers as currently produced, have been practically unchanged in design and material for generations. Although hammers are made in different sizes and the constituent parts, such as the striking head and peen may vary very widely in design, carpenters hammers and ball peen usually comprises heads of various weight and a tapered wooden handle in various lengths. These types of hammers have proven to be generally satisfactory but do present certain disadvantages. In an effective hammer of this type the wood chosen for the handle must be carefully selected and usually is a select grade of hickory or ash. The proper grades ofsuch woods are no longer abundant and cheap as is apparent from the fact that a top grade handle for a one pound machinists hammer cost of the order of twenty-eight cents. An outstanding and universally recognized disadvantage of a wood handle is that, in use the recurrent impact of the hammer head on the work tends to compress the portion of the handle within the head thereby causing it to loosen within the socket, as well as suffering a reduction in strength thus engendering splitting or rupture of the handle in the area of highest stress, that is in the shank section adjacent the hammer head. Despite the use of protective coatings, such as varnishes and the like, the handle will tend to take up and lose moisture depending on ambient atmospheric conditions.

There is thus a real and longstanding need for an improved impact tool, such as machinist hammers, which presents all the advantages of the currently produced wooden handle type but which is more economical to produce and has greater permanency in use. This need is less than adequately satisfied by the recently marketed hammers in which the older wooden handle is replaced by one compose-d of a solid, fiberglass-filled, polyester handle. Such a handle is relatively dense, as compared to its woo-d counterpart, resulting in unbalance of the tool and is impossible to fix securely in the hammer head by orthodox methods.

A primary object of the present invention is to provide an improved impact tool comprised of a striking head and a tubular plastic handle of high impact resistance, relatively low flexure and controlled density which may be secured firmly and permanently in the striking head.

Another object of the invention is to provide a novel portable impact tool incorporating a metallic or nonmetallic head and a tubular, relatively resilient, impactresistant plastic handle.

Yet another object of the invention is to devise an improved method of firmly anchoring a hollow thermo plastic resin handle in a metallic head of a portable impact tool.

An additional object of the invention is markedly to reduce the cost of producing portable impact tools by uniquely associating a hollow thermoplastic resin handle of selected density and physical properties with a metallic tool head.

Further objects and advantages of the invention will become more readily apparent from a consideration of the nature of the invention as exemplified in a preferred embodiment constructed in accordance with the principles of the invention, which embodiment is illustrated in the accompanying drawings in which:

FIG. 1 is a side elevation of a ball peen hammer embodying the principles of the invention, certain parts being broken away to clearly depict the novel features of the invention.

FIG. 2 is an expanded vertical cross-section view of a portion of the structure shown in FIG. 1, illustrating the manner in which the head and handle components are joined together to produce unitary assembly.

FIG. 3 is a top plan view of the hammer head shown in FIG. 1.

FIG. 4 is a side elevation of the head and adjacent portion of the handle shown in FIG. 1.

FIG. 5 is an end view of the front end of the hammer head and assembled handle.

FIG. 6 is a sectional view at the rear end of the hammer head.

FIG. 7 is a perspective View of a non-metallic type wedge shown in FIG. 1, and

FIG. 8 is a perspective view of a modified wedge of metal.

As indicated previously, a typical ball peen hammer currently produced comprises a metallic head, which weighs about 16 ounces, in the eye of which a wooden handle of a length of about 1-3 inches is held in frictional contact by means of inserted wedges of wood or metal. In such a hammer the overall length of the head is about 4 or 4% inches and the width of socket area in the head is about 1 /2 inches. Such heads, as is known are fabricated from cylindrical rod stock by a series of forging operations, usually including initial drop forging in a series of development dies followed by press forging, and then trimming to remove flash and sever the sprue from the head forging. In such hammer heads the eye or socket is generally rectangular in cross-section, although, in some types of smaller size, such as tack hammers, the socket may be formed in oval or ellipsoidal shape. As a general rule in the conventional hammer the sides or opposite walls of the socket are formed with a double taper, usually about 3 in order to provide suificient draft to pull out of the forging die. After removal from the die the flash of such double taper is pierced, so that the cross-section of the socket is double tapered along its length. In sharp contradistinction to such conventional socket design, as will be pointed out more fully hereinafter, hammers produced according to the invention are formed with a socket which is tapered so that the four walls converge from the front face of the head toward the rear face adjacent the handle.

The handle component of the improved portable impact tool comprises a hollow member composed of a selected thermoplastic resin, one end of which is adapted to be inserted within the convergent socket of the head and is forced by an especially conformed wedging member into firm anchorage contact with the head.

Referring now to the drawing an improved tool produced according to the principles of the invention, for exemplary purposes, is illustrated in the form of a ball peen hammer. Such hammer, as shown, comprises three major components, namely, a metallic head, 1, a hollow, thermoplastic resin handle 2 and a spreader or wedge 3 which functions firmly to anchor the handle in the head. In the illustrative embodiment the head 1 is of the bellfaced type incorporating a medial section or poll 4 formed with the laterally extended, hollow shank or eye section 5, which section is integral with a cylindrical flat impact head portion 6, on one side, and with a ball peen section 7 on the opposite. As in typical hammers of this type the shank section 5 merges with the head section 6 and ball peen section 7 along gradually curved, smooth surfaces. The head of the hammer may be fabricated from suitable ferrous or non-ferrous alloys by orthodox forging and/or casting techniques with the notable difference, as contrasted with prior hammers, that the handle-contacting walls of the eye or socket section 5 of the hammer head converge from the front face 8 to the rear face 9. Utilizing currently employed techniques this may be done readily With a suitably shaped plunger and cooperating die blocks. After final shaping the forging is trimmed to remove any flash and to sever the head forging from the sprue and from the cylindrical stock. Alternatively the hammer head may be formed by drop and press forging, trimmed and then subjected to a separate press forging step to form the above described convergent socket. As noted previously in the as-formed head the socket 5 is formed with a double taper: thus is sheared off to provide the desired taper or convergency which in a typical case of a one pound ball peen hammer is about 1.5 taper. It is to be noted that in relatively small hammer heads of such size one cannot have too much taper because it would remove too much metal from the head thus weaken it in the poll section. The taper thus must be held within limits in the smaller size hammer heads; such taper must be suflicient to insure adequate splaying of the end of the handle to lock it in the socket but not so much as to seriously weaken the head. It will be understood that the degree of taper is less critical for hammers of larger size where more leeway on removal of metal from the peen section is permitted.

The handle component 2, as previously mentioned, is composed of a hollow, thermoplastic resin of selected physical characteristics. It has been determined, as a result of considerable research and experimentation, that the most feasible and economical method of producing the handle is by a blow molding technique. This method, as is known, involves the entrapment of an as-extruded soft, hollow body, or parison, of the selected resin in a suitable mold and introducing air under suitable pressure into the lumen of the parison to thereby inflate it into contact with the surfaces of the mold and allowing sufficient time for the plastic material to cool and stiffen to a self-supporting condition while the molding pressure is maintained after which the molded unit is removed and then trimmed to remove flash. It will be appreciated that by invoking the concept of utilizing a hollow plastic handle the total weight and the stress-resistance along its length may be controlled within close limits. By employing such blow-molding technique the handle may be con- 4 formed, in a single step, to any desired shape as shown in FIG. 1, best adapted to insure optimum impact, tensile and compression properties in given sections of the handle by proper design of the mold. Additionally, with a given mold contour or profile the strength of the handle, as in impact tensile and shear, may be widely varied by a predetermined selection or adjustment of the die orifice of the extruder which feeds the parison into the mold to increase or decrease the wall thickness of the parison and commensurately modify the wall thickness of the molded handle. Also by proper design of the handle and conforming the mold correspondingly, hand grips, stiffening ribs as well as esthetic designs can be molded on the handle; the formation of such surfaces on a wooden handle would be impracticable because of the excessive machining cost.

The thermoplastic resin utilized in the fabrication of the handle 2 may be any one of choice which has the desirable characteristics of suitably high impact resistance and flexural strength. Illustrative of such resins suitable for use are homopolymers, unplasticized polyvinyl chloride-acetate copolymers, polyvinyl acetates, suitable polyamides such as nylon, resin-type butadiene styrene copolymers, polyesters, and the like. These are all characterized by low moisture absorption, as compared to wood, and have satisfactory impact resistance, tensile and flexural strength. The preferred resin for the handle is a polycarbonate as produced by blow molding, handles comprised of such resins are most economical as compared to solid wooden or plastic handles. The handle component may be molded in any desired cross-sectional shape and, as noted above, may be of any desired or pre-selected wall thickness. To facilitate the molding operations and to confer optimum structural characteristics on the molded handle, it is found preferable to form the hollow handle in the general shape shown in FIGS. 1, 2 and 4. As there shown the unitary handle embodies a shank portion, designated generally as 2A and an integral, merging handle grip portion 2B. As shown, the handle is generally ellipsoidal in transverse cross-section, having as illustrated in FIG. 5, a relatively long major axis and a relatively short minor axis. The relatively thick-walled shank section 2A merges along a gradual vertical and horizontal taper or slope into the relatively thinner-walled, enlarged ellipsoidal handle section 2B. As in typical hammer handle construction the end of the handle grip section 213 is flared outwardly, as at 2B to insure against slippage of the hand of the user. The handle section 2B may be surfaceembossed in the initial, as-molded form, or embossed subsequent to molding to provide a non-slipping gripping surface. The handle may be formed with one or more longitudinal ribs 10 in the shank section 2A to stiffen this section. As will be seen in FIGS. 1 and 2, the terminal end 11 of the handle is somewhat reduced in cross-section and is provided with the head or other abutments or lip 12 which serves as a stop during assemblage and use of the tool preventing relative longitudinal movement of the hammer head rearwardly of the handle. It is to be observed that the terminal section 11 is slightly longer than the length of socket 5 and when fitted loosely in the socket will project a slight distance beyond the hammer face 8. A typical such handle which has been produced and assembled into a most satisfactory functioning one pound ball peen hammer comprising a unit approximately 13 inches in length below the head in which the stress-taking shank section 2A is about 6 /2 inches long, about of an inch in its major axis and about /3 of an inch in its minor axis and having a wall thickness in the shank section, of about A; of an inch.

The wedging component 3 comprises a solid member of generally ellipsoidal cross section, and corresponding to the cross section of the eye, which converge on a predetermined -0r preselected taper from the front face and towards the rear portion and which taper conforms to that of shank 5. In the preferred form of the invention, as

' shown in FIGS. 2 and 7, the Wedge member 3 is composed of a solid plastic, preferably of the same composition or character as that of the handle 2. In a modified form of the invention, as shown in FIG. 8, the wedge member may be composed of a suitable ferrous or non-ferrous alloy.

The full advantages of inextricably and permanently embodying the handle in the head can best be achieved by employing a specially conformed plastic wedge member and utilizing a novel technique to wedge and/ or Weld it to the contiguous terminal handle portion while expanding or splaying such terminal handle portion into intimate interlocking contact with the encompassing tapered socket of the hammer head. As shown on FIGS. 3 and 7, such wedging member 3 is of generally ellipsoidal cross section each of the walls 13 of which converge from the front face or end 14 towards the rear for a predetermined length and terminates in an untapered end extension 15. The convergent portion of the wedge is formed on a taper of approximately 1.5 more or less, and is coextensive with and conforms to the wall convergence or taper of the socket of the hammer head and is somewhat smaller in cross section than the corresponding por tion of the socket in which it is to be locked. The nontapered wedge extension, as will be observed, in FIG. 2 is adapted to fit within the bore of the handle proximate to the hammer head. This wedge extension 15 preferably is of the order of about /4" long, more or less, for a ball peen hammer, and is but slightly less in cross sectional dimensions than the internal cross sectional dimension of the handle 2A. The wedge 3 preferably is formed with a terminal head 16 at its front end and with a shallow groove or channel 17 for purposes to be more fully described. Upon assemblage of the wedge in the handle in the manner to be more fully described, the extension 15 provides a rigidifying core for the handle in the area adjacent the head serving to limit undue flexure of the bandle under impact or bending stresses encountered in normal use of the tool.

As explained previously, the hammer head is so conformed with relation to the handle 2 and Wedge component 3 as to insure a novel technique of securing the handle fixedly in the shank 5. Unlike prior constructions, the head of the hammer of the present invention is formed with a shank 5 all interior faces or walls of which converge from the front face 8 toward the rear face 9. This convergence of the shank'portion is designed to establish a novel cooperation with the thermoplastic handle and with the wedge 3 to insure a solid and permanent anchor age of the handle in the hammer head.

In assembling the hammer unit, a handle member 2 is positioned in a suitable support frame or jig and a hammer head 1 is slipped down over the reduced handle section 11 so that the rear face 9 abuts the lip 12, and is held centered on the handle by the jig. A wedge member 3 is then wetted with any suitable solvent or cement by dipping the extension end of the wedge into such solution to a depth of about one inch or more. The thus wetted wedge is placed in the bore of the handle section 11 and is forced into the handle by uniformly applied pressure and at a rate that precludes rupture of the plastic or the establishment of fissures in this mass. This may be done safely and expeditiously by forcing the wedge into its anchorage position by means of a hydraulic or pneumatic cylinder. For this purpose a gig comprised of hinged sections adapted to be closed and locked is employed. The interior portion of each section of the gig conforms to and snugly abuts the exterior surfaces of the handle with the lip 12 abutting the forward end of the gig. In this manner the handle is firmly locked against movement during application of pressure. After the wedge is jammed home the sections of the gig are unlocked and the assembled hammer removed.

It will be appreciated that as the tapered wedge is forced lengthwise of the handle the bodied solvent or cement provides inherent lubricity, softens and swells the plastic of the handle and the film of cement on the reduced section of the wedge is wiped backwardly to wet the remainder of the wedge and concomitantly wet and soften the plastic handle enabling the latter to be splayed or spread into intimate mechanical contact with the contiguous surfaces of the shank without rupturing or destroying the integrity of the section 11. It is to be observed that when a solvent is employed the swelling of the material or the handle under the action of the solvent actually applies pressure on the contiguous surfaces of the socket so that, in effect, the method constitutes a type of pressure molding in situ.

In this operation of wedging the handle into the hammer head the two part adhesive system such as polyurethane or epoxies or one part system such as rubber or resinous welding adhesives may be employed. It is also within the purview of the invention to utilize ultrasonic radiations applied to the handle adjacent the head to improve the bond between the handle and head.

It has been found that effective anchorage of the bandle in the head can be achieved by the described technique without employing solvents or adhesives to pre-wet the wedge.

After the assembled unit is removed from the jig, the excess material of the section 11 and wedge 3 which project beyond the front face of the head is ground off to present a curved, smooth surface coextensive with the curved section of the poll. It will be noted at this point that the bead 16, originally formed on the wedge, provides excess plastic material to adequately fill in the area at the front end of the head so that the handle portion of the hammer within the socket area constitutes a solid uniform plastic encapsulate. It will be appreciated that as the tapered wedge is forced lengthwise of the handle plastic will be forced or intruded into firm contact with the adjacent surfaces of the hammer head shank. As the wedge is gradually forced into its ultimate anchoring or locking position the section of the plastic handle within the socket is swaged into the hammer socket by an intrusive or splaying action, insuring intimate contact of the plastic handle portion 11 with all contiguous surfaces of the head shank and wedge and the wedge becomes structurally embodied or locked in the end of the handle. During the gradual ramming-in of the wedge the plastic near the front end of section 11 is forced by the relatively wide end portion 14 into firm contact with the erstwhile spaced convergent surfaces of the eye or socket of the head. When the wedge has been forced into the hollow handle to its maximum extent, the pressure is released and the assembled hammer is removed from the jig.

Utilizing the described method of assembling the head and handle presents may functional advantages. By invoking the swaging technique of intruding the plastic handle section 11 into intimate, firm contact with the contiguous surfaces of the hammer head socket, the end of the handle is in a flared shape and stressed and so structurally embodied in the wedge and head as to obviate the possibility of cold How of the plastic. Since the anchorage portion of the handle is a divergent section firmly abutting and locked to the convergent head socket there is no possibility of longitudinal displacement of the handle rearwardly of the head under the action of centrifugal or other forces incident to normal swinging operations of the hammer. The unstressed handle portion adjacent the hammer socket is mechanically rigidified by the integral wedge section 15 providing an eminently rugged structure while at the same time insuring a preselected optimum resilience in the handle coupled with controlled ultimate flexure established by the portion of the wedge 15 which extends into the bore of the handle proximate the hammer head. Since the flared anchorage end of the handle is interposed throughout between the head and wedge the hammer assembly is most effective in absorbing the shock of impact as well as secondary or harmonic vibrations developing therefrom.

The major advantages of the invention may be achieved by utilizing a metallic wedging member in lieu of the plastic type. As shown in FIG. 8, such a unit is of the same size and shape as the plastic wedge previously described having side walls 13 and an untapered extension 15. It will be noted that the exterior surfaces of the wedge lying within the socket area are formed with reentrant surfaces 18, such as serrations, indentations or cusps.

In assembling a hammer using a metallic wedge the same general procedure previously described is followed. It is however desirable to heat the section 11 of the handle to render it sufficiently ductile to insure its expansion into firm contact with the walls of the hammer socket. This may be done by heating the section 11 directly or by preheating the hammer head and/ or wedge. The wedge is forced to its anchorage position by smoothly and gradually applied pressure and at a rate that precludes rupture of the plastic handle. As the tapered wedge is forced lengthwise of the handle, the plastic is intruded into firm contact with the adjacent surfaces of the shank on the one hand and into the serrations 18 of the wedge on the other. Upon cooling after assemblage, wedge becomes permanently structurally embodied or locked in the set, flared end of the handle.

It will be understood that within the basic concept of the invention many modifications may be made. Thus, if desired, the internal faces or bore of socket may be formed with a series of reentrant surfaces or bights similar to those formed on the wedge but offset with respect thereto to enhance the locking action of effect. Also, if desired, prior to the introduction of the handle into the socket the interior surfaces of the socket may be coated with a suitable metal-to-plastic adhesive or cement to increase or supplement the anchorage effect. Again the hollow handle may if desired be rigidified throughout its length as by means of a hollow metal insert of selected dimensions one end of which abuts the terminal interior face of handle portion 2B and the other end of which enclosed all or a portion of the straight wedge extension 15.

While for purposes of illustration the principles of the invention have been described as embodied in a machinists hammer it will be appreciated that it is of similar utility and advantage in a wide variety of portable impact tools having striking and/ or peening and/ or cutting heads such as carpenters, blacksmiths and bricklayers hammers, hatchet, axes and the like. The useful scope of the invention is thus to be considered as not limited to the particular illustrative embodiment shown except as such limitations are clearly imposed by the appended claims.

I claim:

1. An improved portable impact tool comprising a striking head formed with a handle-receiving socket extending through the head, all surfaces of said socket converging from the front to the rear of the head and a preformed hollow thermoplastic resin handle, said handle having a terminal divergent flared section tightly abutting all contiguous surfaces of said socket and a wedge member having a convergent section within and abutting the contiguous surfaces of the flared section of the handle.

2. An improved portable tool comprising a striking head formed with a through handle-receiving socket, all surfaces of the socket converging from the front to the rear of the head and a preformed tubular thermoplastic resin handle, said handle having a flared terminal section fitting within the socket and firmly abutting all contiguous surfaces of the socket and a wedge member having a divergent section within and bonded to the flared section of the handle.

3. An improved portable impact tool comprising a metallic striking head formed with a through handlereceiving socket the surfaces of which converge from the front to the rear of the head; a premolded hollow, thermoplastic resin handle having an outwardly flared terminal portion fitting within and firmly abutting all the contiguous surfaces of the socket and a wedge member having a convergent section coextensive with and conforming to the convergent socket within and adhesively bonded to the interior of the flared section of the handle.

4. An impact tool according to claim 3 in which the Wedge member is formed of a resin.

5. An impact tool according to claim 3 in which the wedge member is formed with an untapered extension received within the handle adjacent the said flared terminal portion.

6. An improved impact tool comprising a metallic striking head formed with a through handle-receiving socket, which socket converges from the front to the rear face of the head; a preformed hollow thermoplastic resin handle having a flared terminal portion fitting within the socket and a wedge member having a swaging portion within the confines of the said flared portion and an integral straight extension projecting a substantial distance into and in close proximity to the adjacent interior surface of the hollow handle, the said swaging portion of the wedge member converging from the front to the rear face of the head and confining the terminal portion of the handle within the socket.

7. An impact tool according to claim 6 in which the convergent portion of the wedge and extension sections are autogenously bonded to the contiguous surfaces of the handle.

8. A method of producing improved portable impact tools which tools embody essentially a striking head formed with a handle-receiving socket and a relatively elongated, hollow thermoplastic resin handle having an end section receivable in a socket, the improvement which comprises: forming the head with a through socket the walls of which converge from the front to the rear face of the head; preforming a hollow thermoplastic handle; inserting an end portion of the handle into the head socket, wetting a wedge member with a resin solvent and forcing said lubricated wedge member under gradually applied pressure into the bore of the end portion of the handle to distort contiguous surfaces of the thermoplastic handle within the socket into firm mechanical contact with all the surfaces of the socket, thus forming a firm lock of the handle on the head.

9. A method of producing improved portable impact tools which tools embody essentially a striking head formed with a handle-receiving socket and a relatively elongated, hollow thermoplastic resin handle having an end section receivable in the socket, the improvement which comprises: forming the head with a through socket the walls of which converge from the front to the rear face of the head; preforming a hollow thermoplastic handle; inserting an end portion of the handle into the head socket; wetting at least a portion of a wedge member with a resin solvent and forcing said lubricated wedge member under gradually applied pressure into the bore of the end portion of the handle to distort contiguous surfaces of the thermoplastic handle within the socket into firm mechanical contact with all the surfaces of the socket, thus forming a firm lock of the handle on the head.

References Cited UNITED STATES PATENTS 2,846,277 8/1958 Marsh 29 FOREIGN PATENTS 1,369,164 6/1963 France.

865,287 4/ 1961 Great Britain.

WILLIAM FELDMAN, Primary Examiner.

R. V. PARKER, IR., Assistant Examiner. 

1. AN IMPROVED PORTABLE IMPACT TOOL COMPRISING A STRIKING HEAD FORMED WITH A HANDLE-RECEIVING SOCKET EXTENDING THROUGH THE HEAD, ALL SURFACES OF SAID SOCKET CONVERGING FROM THE FRONT TO THE REAR OF THE HEAD AND A PREFORMED HOLLOW THERMOPLASTIC RESIN HANDLE, SAID HANDLE HAVING A TERMINAL DIVERGENT FLARED SECTION TIGHTLY ABUTTING ALL CONTIGUOUS SURFACES OF SAID SOCKET AND A WEDGE MEMBER HAVING A CONVERGENT SECTION WITHIN AND ABUTTING THE CONTIGUOUS SURFACES OF THE FLARED SECTION OF THE HANDLE. 